HeySpace - HeySpace is the only free task and simple project management software with communication and collaboration feature.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
P2 - Share, discuss, and collab with your team. By Wordpress.
Event Hunt - Startups and Tech Events Curated By Locals
Slack - A messaging app for teams who see through the Earth!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets